Bayer Aktiengesellschaft

Bayer Cropscience Ag

Wolfram Sirges

Kai Van Laak

Rolf Grosser

Armin Heyn

Dieter Arlt

Burkhard Kohler

Detlef Wollweber

Walter Lange

Claus Dreisbach

Thomas Prinz

Christian Laue

Michael Grosse-Bley

Guido Giffels

Torsten Pohl

Uwe Zweering

Jörn Stölting

Axel Eble

Bruno Bomer, Deceased

Ulrich Schwiedop

Torsten Taschner

By Guido Bomer

The present invention pertains to a process for the production of a specific crystal modification of a polymorphic, organic substance by precipitation of the specific crystal modification from the aqueous solution of the salt of the polymorphic substances using ordinary water-soluble organic solvents as additives as well as an acid or base.

Method for producing specific crystalline modifications of polmorphous substances

The present invention relates to a process for the preparation of compounds of the formula (I)by reacting compounds of the formula (II)in which

Method for producing 1,3-disubstituted 2-nitroguanidines

The present invention relates to a novel process for the preparation of N-methyl-N&prime;-nitroguanidine by reacting nitroguanidine with aqueous methylamine solution buffered by the addition of inorganic or organic acids.

Method for producing N-methyl-N&prime;-nitroguanidine

The invention relates to a novel process for preparing optically active trimethyllactic acid and/or its esters by catalytic hydrogenation of trimethylpyruvic acid and/or its esters in the presence of noble metal complex catalysts containing phosphorus ligands.

Process for preparing optically active trimethyllactic acid and its esters

Method for production of 1,3-disubtituted 2-nitroguanidines

The invention relates to the preparation of enantiomerically pure bis-diphenylphosphine oxides in a particularly advantageous manner by (1) reacting an aromatic bromine compound with a diphenylphosphinic chloride in a mixture of tetrahydrofuran and an aromatic hydrocarbon to give a diphenylphosphine oxide, which is isolated from a solution in an aromatic hydrocarbon by adding a saturated aliphatic hydrocarbon; (2) metalating the resulting diphenylphosphine oxide in the 6-position and reacting the metalated diphenylphosphine oxide with iodine at temperatures not less than &minus;25&deg; C. in such a way that a small amount of iodine is always present in excess, giving a 2-iodo-diphenylphosphine oxide; (3) preparing a racemic bis-diphenylphosphine oxide from the resulting 2-iodo-diphenylphosphine oxide using copper and an aromatic hydrocarbon solvent and crystallizing the racemic bis-diphenylphosphine oxide from a solution in an aromatic hydrocarbon; and (4) separating isomers using an enantiomerically pure mono- or dicarboxylic acid to obtain a first enantiomer by crystallization from a solution in an aromatic hydrocarbon and obtaining a second enantiomer by hydrolysis and subsequent crystallization from a solution in an aromatic hydrocarbon.

Process for the preparation of enantiomerically pure (5, 5&prime;-dichloro-6,6&prime;-dimethoxy-biphenyl-2,2&prime;-diyl)- bis(diphenylphosphine oxides)

The invention relates to chiral polymers which are bonded to a support and have improved properties, a process for the preparation of these materials and their use as chiral stationary phases in the chromatograhic separation of optical isomers, in particular of racemates into their enantiomers.

Chiral stationary phases for chromatographic separation of optical

The invention relates to novel bisphosphonates and to processes for their preparation and for their resolution into the enantiomers. The bisphosphonates according to the invention are valuable intermediates for the preparation of bisphosphine compounds, especially chiral bisphosphine ligands. These in turn are constituents of transition metal complexes which are used as catalysts inter alia in asymmetric hydrogenation. The novel bisphosphonates have the general formula (I) ##STR1## in which R.sup.1 is linear or branched alkyl having up to 6 carbon atoms, aryl or aralkyl, each of which can optionally be substituted, or two radicals R.sup.1 together are a bridging hydrocarbon radical having up to 6 carbon atoms,

Intermediates for the synthesis of bisphosphine compounds

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Düsseldorf, Germany

Wolfram Sirges